Sewage sludge charcoal production by N2- and CO2-torrefaction
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Subtitle: Sewage sludge charcoal production by N2- and CO2-torrefaction
Author list: Ntuli, Freeman
Publisher: Elsevier
Publication year: 2017
Journal: Journal of Environmental Chemical Engineering (2213-2929)
Volume number: 5
Issue number: 5
Start page: 4406
End page: 4414
Number of pages: 9
ISSN: 2213-3437
URL: https://www.sciencedirect.com/science/article/pii/S2213343717303858?via=ihub
Languages: English-United States (EN-US)
Abstract
The production of sewage sludge charcoals under N2 and CO2 as torrefaction atmosphere and their subsequent combustion was compared in this work. The experiments were carried out in a Thermogravimetry-Infrared Spectrometry (TGA-FTIR) analyser and a laboratory scale furnace. High temperatures (230-480 °C) were considered in order to study the removal of N- and S-compounds, one of the main concerns for the thermal valorisation of sewage sludge. Torrefaction treatment at 330 °C under N2 produced a charcoal with a 34% reduction in weight. The release of SO2 during the combustion of this charcoal was negligible and the release of NH3 and COS was reduced by half (46% for NH3 and 52.5% for COS) compared with the combustion of raw sewage sludge. The pollutant removal improved with torrefaction temperature and the charcoal produced at 480 °C released a negligible amount of NH3, COS and SO2 during combustion. The CO2 used as torrefaction atmosphere exhibited a reactive behaviour in the FTIR-TGA analyser, increasing the weight loss rate and shifting the characteristic degradation peak to a temperature around 7 °C lower. Besides, the charcoals produced under CO2 exhibited a less reactive behaviour. Overall, the results here presented prove that the CO2 influences slightly the torrefaction mechanisms and the properties of the sewage sludge charcoals produced. © 2017 Elsevier Ltd. All rights reserved.
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